Yiran Liang

A novel magnetic ionic liquid modified carbon nanotube for the simultaneous determination of aryloxyphenoxy-propionate herbicides and their metabolites in water

A reliable, sensitive, rapid and environmentally friendly analysis procedure for the simultaneous determination of the analytes with a wide range of polarity in the environmental water was developed by coupling dispersive magnetic solid-phase extraction (d-MSPE) with high-performance liquid chromatography (HPLC)-diode array detector (DAD) and ultra-high pressure liquid chromatography (UHPLC)-triple quadrupole mass spectrometer (MS/MS), in this work. Magnetic ionic liquid modified multi-walled carbon nanotubes (m-IL-MWCNTs) were prepared by spontaneous assembly of magnetic nanoparticles and imidazolium-modified carbon nanotubes, and used as the sorbent of d-MSPE to simultaneously extract aryloxyphenoxy-propionate herbicides (AOPPs) and their polar acid metabolites due to the excellent π-π electron donor-acceptor interactions and anion exchange ability. The factors, including the amount of sorbent, pH of the sample solution, extraction time and the volume of elution solvent were investigated. Under the optimized conditions, the proposed d-MSPE coupling to HPLC-DAD system had a satisfactory performance, the limits of detection (LODs, defined as the signal to noise ratio of 3) and the limits of quantification (LOQs, defined as the signal to noise ratio of 10) for analytes in Milli-Q water were in the range of 2.8-14.3 and 9.8-43.2 μg L(-1) respectively. Calibration curves were linear (r(2)>0.998) over the concentration range from 0.02 to 1 mg L(-1). The recoveries of the eight analytes ranged from 66.1 to 89.6% with the RSDs less than 8.6%. In order to extend the method in extremely low concentration analysis, d-MSPE-UHPLC-MS/MS was investigated, which showed better performance in terms of limit of detection and analysis time.

Nonoccupational Exposure to Pyrethroids and Risk of Coronary Heart Disease in the Chinese Population

Pyrethroids and the metabolites have been frequently observed in the environment. Animal data suggests that pyrethroids can induce adverse effect on the cardiovascular system but there are no human studies examining pyrethoids exposure as a risk for coronary heart disease (CHD). We analyzed three nonspecific pyrethroids metabolites in urine and studied the association with CHD risk. A total of 72 CHD patients and 136 healthy subjects were recruited in Shanxi province in China from 2013 to 2014 by matching age and gender. The median concentrations of urinary cis-CDDA (cis-3-(2,2-dichlorovinyl)-2,2-dimethyl cyclopropane carboxylic acid), trans-CDDA (trans-3-(2,2-dichlorovinyl)-2,2-dimethyl cyclopropane carboxylic acid) and 3-PBA (3-phenoxybenzoic acid) among healthy subjects were 1.03, 0.42, 0.74 μg/L respectively, while the median concentrations of the three metabolites among CHD patients were 1.93, 1.07, 1.09 μg/L respectively, significantly higher than healthy subjects. Upper tertile of urinary pyrethroid metabolites were associated with an increased risk of CHD compared with the lowest tertile (cis-CDDA: ORT3vsT1 = 6.86, 95% CI: 2.76-17.06, p-trend = 0.000; trans-CDDA: ORT3vsT1 = 6.94; 95% CI: 2.80-17.19; p-trend =0.000; 3-PBA: ORT3vsT1 = 3.62; 95% CI: 1.48-8.88; p-trend = 0.009; total pyrethroid metabolites: ORT3vsT1 = 4.55; 95% CI: 1.80-11.54; p-trend = 0.002). This study provides information on pyrethroids exposure in China and reveals a possible positive association between pyrethroids exposure and the risk of coronary heart disease.

Synthesis of novel β-cyclodextrin functionalized S, N codoped carbon dots for selective detection of testosterone

A novel functionalized carbon dot has been synthesized by covalently linking β-cyclodextrin to the surface of N, S codoped carbon dots (β-CD-CDs). The characterization was confirmed by transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectra, ultraviolet-visible, and fluorescence emission spectra. On the basis of this carbon dot and (ferrocenylmethyl) trimethylammonium iodide (Fc+), a photo-induced electron transfer (PET) fluorescent probe system was developed to determine the concentration of testosterone in water and identify testosterone in cell by fluorescence imaging as a visible biomarker. Under the optimum condition, the fluorescent intensity of the probe system linearly responded to the concentration of testosterone from 0μM to 280μM and the limit of detection was 0.51μM. This probe system also performed well at determining testosterone in groundwater with average recoveries of testosterone ranging from 96% to 107% at spiking levels of 0.5-100μM, and the relative standard deviation remained below 13%, which provided a reliable, rapid and easy method to determine testosterone in environmental water. Furthermore, the low cytotoxicity, high anti-interference ability, and excellent biocompatibility of β-CD-CDs made this probe system successfully used in cell fluorescence imaging to monitor levels of testosterone in the cytoplasm of cells with a promising application value in medical research.

Enantioselective metabolism of quizalofop-ethyl in rat.

The pharmacokinetic and distribution of the enantiomers of quizalofop-ethyl and its metabolite quizalofop-acid were studied in Sprague-Dawley male rats. The two pairs of enantiomers were determined using a validated chiral high-performance liquid chromatography method. Animals were administered quizalofop-ethyl at 10 mg kg−1 orally and intravenously. It was found high concentration of quizalofop-acid in the blood and tissues by both intragastric and intravenous administration, and quizalofop-ethyl could not be detected through the whole study which indicated a quick metabolism of quizalofop-ethyl to quizalofop-acid in vivo. In almost all the samples, the concentrations of (+)-quizalofop-acid exceeded those of (−)-quizalofop-acid. Quizalofop-acid could still be detected in the samples even at 120 h except in brain due to the function of blood-brain barrier. Based on a rough calculation, about 8.77% and 2.16% of quizalofop-acid were excreted through urine and feces after intragastric administration. The oral bioavailability of (+)-quizalofop-acid and (−)-quizalofop-acid were 72.8% and 83.6%.

Enantioselective metabolism of the chiral herbicide diclofop-methyl and diclofop by HPLC in loach (Misgurnus anguillicaudatus) liver microsomes in vitro

An efficient and reliable enantioseparation method by high-performance liquid chromatography (HPLC) for the chiral herbicide diclofop-methyl (DM) and its primary metabolite diclofop (DC) was developed and validated, and the biological process of the enantiomers in loach liver microsomes (LLM) in vitro was investigated. The enantiomers of DM and DC were first separated on an immobilized-type stationary phase of Chiralpak IC. The best resolutions were achieved under the chromatographic condition of n-hexane/IPA/TFA 96:4:0.1(v/v/v) at 20°C with each Rs>2 and the two pairs of enantiomers could be eluted in about 10min. The extraction recoveries of the analytes from LLM were 79.6-108.9% with RSD≤11.5%. The enzyme kinetics of DM enantiomers were different, with the Km value 320.7 for (S)-DM and 392.1 for (R)-DM. The metabolism experiment in vitro showed DM underwent a rapid phase-I metabolism with or without NADPH, indicating the esterases in liver played a dominant role. No interconversion between the two enantiomers was observed by single-enantiomer incubation. The preferential degradation of (S)-DM was confirmed with the half-time (t1/2) of (S)-DM 5.27min and 21.2min for (R)-DM. DC enantiomer was generated by its corresponding ester form and could not be further degraded during the incubation. It was the first study on biotransformation of DM and DC enantiomers in LLM in vitro. The results may help to evaluate the ecological risks of chiral pesticides.

Effects of wastewater irrigation and sewage sludge application on soil residues of chiral fungicide benalaxyl

The effects of wastewater irrigation and sewage sludge on the dissipation behavior of the fungicide benalaxyl and its primary metabolite benalaxyl acid in soil were studied on an enantiomeric level during a 148-day exposure experiment. Chiral separation and analysis of the two pairs of enantiomers were achieved using HPLC-MS/MS with a chiralpak IC chiral column. Benalaxyl decreased with half-life of 16.1 days in soil under tap water irrigation with preferential residue of S-benalaxyl. Benalaxyl acid was formed with great preference of R-enantiomer before 21 days while enriched in S-enantiomer afterwards. The degradation of benalaxyl was restrained by both wastewater and treated wastewater irrigation, but the enantioselectivity in S-benalaxyl residue was enhanced. Benalaxyl acid was also formed with similar enantioselectivity as in tap water irrigation. Sewage sludge could accelerate benalaxyl degradation with shorter half-life. Surprisingly, the enantioselectivity with preference degradation of S-enantiomer in sewage sludge was opposite to that in soil. More benalaxyl acid was generated with EF values always lower than 0.5 and remained longer in sewage sludge than in soil. A sterilization experiment indicated that the conversion of benalaxyl to benalaxyl acid and the enantioselectivity were determined by the microorganisms in soil or sewage sludge. Farming practices like wastewater irrigation and sewage sludge application might not only influence the fate of pesticide, but also the enantioselectivity of chiral pesticide enantiomers and thus the risks of pesticide residues posed to the environment.

Stereoselective metabolism of the UV-filter 2-ethylhexyl 4-dimethylaminobenzoate and its metabolites in rabbits in vivo and vitro

The stereoselective metabolism of the enantiomers of the UV-filter 2-ethylhexyl 4-dimethylaminobenzoate (EDP) in rabbits was studied. The two major metabolites 4-(N,N-dimethylamino) benzoic acid (DMP) and 4-methylaminobenzoic acid (MMP) were also investigated in vivo and in vitro. Cytotoxicity of EDP and its two metabolites was also investigated in hepatocytes. The results showed that EDP degraded rapidly to its metabolites (DMP and MMP) and could not be detected in blood at 5 min after intravenous administration to rabbit in vivo. In almost all the tissue samples, EDP, DMP and MMP could not be detected at 3 h expect DMP was found in the liver and kidney at about 1 mg kg−1 level. EDP was found to be degraded to DMP rapidly in plasma and liver microsome in vitro with t1/2 less than 20 and 5 min and the whole process was enantioselective with preference of (+)-form. DMP was observed to be further degraded to MMP in liver microsome in the presence of NADPH. The cytotoxic effects of EDP, DMP and MMP were carried out using buffalo rat liver cell line. The results from cell viability assays indicated that the degradation of EDP was a detoxification process.

Enantioselective behaviour of the herbicide fluazifop-butyl in vegetables and soil

The enantioselective dissipation of the enantiomers of fluazifop-butyl in tomato, cucumber, pakchoi, rape and soil under field condition was investigated to elucidate the enantioselective environmental behaviours and chiral stability of the optical pure product. Fluazifop, the major chiral metabolite of fluazifop-butyl, was also detected. Fluazifop-butyl dissipated rapidly in the vegetables and soil with the half-lives of the enantiomers ranging from 1.62 to 2.84days. Enantioselective degradations of fluazifop-butyl were found. In tomato and cucumber, S-fluazifop-butyl dissipated faster than R-enantiomer, while R-fluazifop-butyl showed a faster degradation in pakchoi, rape and soil. Fluazifop was found almost immediately after the application of fluazifop-butyl and had relatively longer persistent time. When the optical pure product fluazifop-P-butyl was applied, rapid degradation to R-fluazifop was found with half-lives from 1.24 to 2.28days, and no S-fluazifop-butyl or S-fluazifop was detected showing the herbicidally active fluazifop-P-butyl and R-fluazifop were configurationally stable.

Organochlorine pesticide acetofenate and its hydrolytic metabolite in rabbits: Enantioselective metabolism and cytotoxicity

Acetofenate (AF) is a chiral organochlorine pesticide used for controlling hygiene pests. In this study, the metabolism of AF in rabbits in vivo and in vitro was investigated and the primary chiral metabolite acetofenate-alcohol (AF-A) was analyzed. The cytotoxicity of AF and AF-A was also determined. AF in rabbits in vivo was eliminated so rapidly that AF could not be detected within 10min after intravenous administration at 20mg/kg (body weight), and AF-A was quickly formed. In vitro metabolism assay, using plasma and liver microsomes, showed that AF was also quickly metabolized to AF-A and the metabolic process was significantly enantioselective with preferential degradation of (-)-AF and formation of (-)-AF-A. The cytotoxicity of AF and AF-A were investigated by assessing cell proliferation, apoptosis and generation of reactive oxygen species. The results showed that AF and AF-A induce enantioselective cytotoxicity. This study will be helpful for improving knowledge about the metabolism and toxicity of AF on an enantiomeric level and providing evidence to understand the potential environmental risk.

Absorption, Distribution, Metabolism, and in Vitro Digestion of Beta-Cypermethrin in Laying Hens

Beta-cypermethrin (beta-CP), an important pyrethroid insecticide, and its main acid metabolites are frequently detected in human samples. Because beta-CP may pose some risk to human health, we studied dynamics and residues of beta-CP and its metabolites in hen egg, droppings, blood, and 15 other tissues after continuous exposure. A digestive model was then used to study beta-CPs digestive fate. Beta-CP and its metabolites significantly accumulated in tissues with high lipid contents and were readily transferred to eggs. Beta-CP was mainly metabolized into acid metabolites that accumulated in egg and edible tissues of laying hens, suggesting that humans may be exposed to beta-CP acid metabolites through food.